Effect of TiO2 buffer layer on the structural and optical properties of ZnO thin films deposited by E-beam evaporation and sol–gel method

In this work, TiO2 buffer layers were first deposited on Si substrates by electron beam evaporation, and then ZnO thin films were deposited on TiO2 buffer layers by electron beam evaporation and a sol–gel method, respectively. The structural features and surface morphologies of these films were analyzed by X-ray diffraction (XRD) and a scanning probe microscope (SPM), respectively. The photoluminescence (PL) spectra were measured by a fluorophotometer. The analyses of the structures and surface morphologies showed that all the ZnO thin films were preferentially oriented along the c-axis perpendicular to the substrate surface; TiO2 buffer layers increased the intensity of (0 0 2) diffraction peaks, made the grains denser and the surfaces of the films smoother. The photoluminescence spectra showed that TiO2 buffer layers enhanced ultraviolet emissions and reduced visible emissions of the ZnO thin films to a large degree. All the results suggested that the use of TiO2 buffer layers effectively improved the quality of ZnO thin films.